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Measuring and Modelling PM Levels on Underground Platforms

Time: Fri 2022-01-28 14.00

Location: F3, Lindstedtsvägen 26 & 28, Stockholm

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Language: English

Subject area: Machine Design

Doctoral student: Minghui Tu , Tribologi, Maskinkonstruktion (Avd.)

Opponent: Dr Teresa Moreno, Institute of Environmental Assessment and Water Research

Supervisor: Professor Ulf Olofsson, Tribologi, Maskinelement, Järnvägsgruppen, JVG, Maskinkonstruktion (Avd.)

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Urban railways have become an essential part of the transportation network of cities due to their convenience and high capacity. To make full use of urban space, many urban railway platforms are built underground. However, according to local surveys and studies, the concentration of airborne particles on underground platforms is significantly higher than that of particle concentrations aboveground. These platform particulates are often rich in heavy metal elements such as iron, copper and manganese, which may adversely affect the health of commuters riding urban railways. Therefore, the primary purpose of this research is to explore various factors that affect the airborne particle concentrations on urban underground railway platforms and then provide some suggestions for improving the air quality of the urban railway commuting environment.

The papers appended are all based on the analysis of field measurements on the Stockholm urban railway platforms in Sweden between 2016 and2020 (Paper A to E). According to different research purposes, diverse statistical models have been established. By exploring the model parameter factors, it is possible to quantify the airborne particle concentrations on underground platforms. The thesis started with the qualitative trend between train movement and platform particle concentration and found that train operation and braking are closely related to the increase in platform particle concentration (Paper A). Then, by comparing linear and non-linear train frequency and particle concentration relationship models, the critical direction for studying the train frequency factor using the linear model was determined (Paper B). After that, the train frequency factor was deconstructed into two approaches. Namely, train brake effect factor, train accumulative effect factor (Paper C) and equivalent train frequency factor, train-type factor (Paper D and E). Finally,non-train-related elements were added to the train-related model as an extension (Paper E). A preliminary quantitative study of non-train-related factors was conducted.

Based on the above research results, this thesis proposes three possible methods to improve the air quality of underground platforms. These consist of: replacing train types that emit higher particles with those that emit lower ones; deploying the intelligent control ventilation system; and adding night cleaning in the underground system.